The status of abalone culture in China.docx
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The status of abalone culture in China.docx
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ThestatusofabalonecultureinChina
ThestatusofabalonecultureinChina
ABSTRACTSince1990abaloneculturehasspreadwidelyfromnorthtosouthonChina'scoast.Estimatedtotalyieldfortheyear2001wasaround4,500tonnes(excludingTaiwan).Thereareseveralhundredsofabalonefarmsalongthecoast.Someofthebiggerfarmsproducemorethan100tofliveabaloneeachyear.ThemainculturedspeciesareHaliotisdiversicoloraquatilisReeveinthesouthandH.discushannaiInointhenorth.AdditionallyH.discusdiscussReevehasbeenintroducedfromJapanandhybridizedwithH.discusshannai.Crossbreedinghasbeenappliedinproduction.Tankcultureandfloatingraftmethodsareimportantinthesouthandnorthrespectively.Atpresent,epidemicvirusdiseasesandVibrioarethegravestthreat.Farmshavesufferedheavyeconomiclossesasaresultofthese.
KEYWORDS:
abalone,culture,China
INTRODUCTION
SincethepreviousreviewofabalonecultureinChina,writtenforthe1989FirstInternationalSymposiumonAbaloneBiology,FisheriesandCulture(Nie1992)therehasbeendramaticchange.AbalonecultureinamassscaleinChinabeganinthemid1980s.Itdevelopedrapidlyinthe1990sspreadingalongthecoastsfromnorthtosouth.Estimatedabaloneoutputwasabout4,500tonnes(excludingTaiwan)in2001,99%producedbycultivation.Haliotisdiversicoloraquatilis(i.e.,H.diversicolorsupertexta)wasaround65%ofthetotalyield.Theculturedspeciesarevaried.Thetechniqueofcrossbreedinghasbeenusedwidely(Nieetal.1995a,Nie&Wang2000).Triploidbreedinghasalreadystartedinproductionsituations(Wangetal.1990,Sunetal.1993,Sunetal.1998,Zhangetal.1998).Becausetheabaloneindustryhasdevelopedrapidlysalespriceshavedeclinedsharply.Thishasbeenespeciallysoforthepriceofsmallabalone.ForexampleH.diversicoloraquatilissalespricehasbeensometimeslessthanthecostofproduction.Epidemicdiseaseshaveoccurredfrequentlysince1993(Liuetal.1995,Nieetal.1995a,Maetal.1996).Inparticularavirusdiseasehasappearedsuccessivelyduringlatewinterinthesouthsince1999(Huangetal.1999).Farmshavesufferedheavylossesandthevirusisaseriousthreatforabalonecultureatpresent.
CulturedSpeciesandDistribution
ThereareeightspeciesofabalonealongChina'scoasts.GeographicallyH.discushannaiInoistheonlyspeciesinLiaoningandShandongProvincesinnorthernChina.TheothersevenspeciesaredistributedinFujian,Taiwan,Guandong,andHainan,thesouthernprovinces.ThesespeciesareH.diversicolordiversicolorReeve,H.diversicoloraquatilisReeve,H.variaLinnaeus,H.planataSowerby,H.ovinaGmelin,H.clathrataReeve,andH.asininaLinnaeus(Lu1978,Dai&Wu1989).BecauseH.diversicolordiversicolorgrowsslowly,H.diversicoloraquatilisbecomesveryimportant.ThisspecieswasintroducedfromTaiwantothesoutherncontinentalcoastsin1989andisnowraisedwidelythere.AdditionallyH.discusdiscusReevewasintroducedfromJapanin1986,H.discushannaiInofromDalianin1990andtheirhybridizedgenerationareraisedinthemidandnorthernFujian(Nieetal.1995b).TherearenowseveralhundredsofabalonefarmsinChina.Thelargestproducemorethan100tonnesofliveabaloneperyear.
CultureMethods
TheculturemethodsusedinChinaarequitevaried.Becauseofthecoastalandclimaticconditionstheyaredifferentinthenorthandsouth.Longlineraftisanimportantmethodinthenorth.Alengthof60-80mofropetiestogetherplasticfloatingglobestosupportcages.Therearetwosortsofcagecurrentlyinuse.Aspecialcageforabalonecultureconsistsof6-12tiersof60-cmdiameterplasticdishes.Theentireassemblyiscoveredwithanetsealedwithazipper.Thesecondtypeusedisascallopcage,of8-12tiersof33-cmdiameter.Mostraftsaremixedculturewithabaloneandalgalfood,LaminariaorUndaria.Raftsarealsousedinsomebaysinthesouthwherethewindandwavesareweak.Intheseinstancesaplasticbasket,thesameasindoortankculturebaskets,isusedinsteadoftheothercages.
Tankcultureonlandisthemaintypeinthesouth.Becauseoffrequenttyphoonstheculturehadtodeveloponland.Concretetanksareusedofaround30-50cubicmeters.AdarkPVCbasketof40cmx30cmx13cmisincommonuse,usuallyinastackof8-12tiersarrangedinrowsinatank.Thebasketsoccupy40-70%ofthetankcapacity(Nie&Wang2000).
InthewesternGuangdongandHainanProvince,inrecentyears,smallabaloneareculturedintheintertidalzone.Atypeofcylindricalconcretecase,110cmx80-120cm(h)withanironrackandnetinside,issetonalowintertidalzone(Cai&Huang2000).
Rockyintertidalzonesinthenortharealsoused.Heregrowersbuildframesandcoverwithnetaswellasothertypesofcages(Zhangetal.1994).
BreedingTechniquesandPresentProblems
Therearesomedifferencesinbreedingtechniques.ThemethodsinthenortharesimilartoJapanesemethodsinmanyways,andinthesouththemethodsapproximatethoseofTaiwan.
Allhatcheriesinthenorthmaintainparentstockwithelevatedtemperature(20[degrees]C)inwinterandinducespawninginspring.Thisallowssufficientwarmweatherforgrowinglargerseed(to>15mm)beforethecomingwinter.IncontrastthesmallabalonecaninducespawningnaturallyfromMaytoDecember(mainseasonisSeptembertoNovember)inthesouth.NonethelesssomefarmsinthesouthalsomaintainparentanimalswithelevatedtemperatureinwinterandinducespawningfromApriltoJune.
Thesubstrateforlarvalsettlementinthenorthisacorrugatedplasticplate(40cmx31cm)heldinracks.Variationsappearinthesouthernfarms.Mostfarmspreferatransparentplasticsleet(60cmx40cm)frequentlysetupsothatmanyplasticsheetsarehungunderawoodenbar.Othertypesofmembrane(ratherthanracked)corrugatedplatesarealsoused(Nie&Wang2000).
AmethodofspawninginductionwithUVlightandwatertemperaturealteration(3[degrees]Cto5[degrees]C)iscurrent.Inthenorth,thefertilizedeggsaremaintainedtothepostveligerstageandthenputintoatankforsettlement.Inthesouthitismorecommontoplacefertilizedeggsdirectlyinasettlingtank,withnowaterexchangeuntillarvalsettlement.Fromtheviewpointofmassproductionthelatterisquitefeasiblebecauseitsavesalotoflabor,time,andfacilities.
Theyoungjuvenilesareremovedfromthetransparentplate/membraneat2-4mm,amuchsmallersizethanduringtheearlyyearsofabalonecultureinChina.Commonly,inthenorth,thejuvenilesarethentransferredinaboxnetwithadarkplateonthenetbottom.Inthesouththeyareraiseddirectlyonthebottomofanothersettlingtank,onasubstrateofsquarebrickswithshortlegsthatarearrangedacrossthebottomofthesettlingtanks.Thedensityofrearingisaround3,000-5,000juvenilespersquaremeter.Asurvivalrateofabout40%to60%isobtainedandmeasuredfromtheremovalphase(2-4mm)uptotheendofnurseryrearing(20mm),inthesouth.Afullcycleofnurseryrearingtakesabout6-8mowithameanproductionrateinallsettlingtanksof2,000-3,000seed.[m.sup.-2].
PresentProblems
InrecentyearsthenurseryrearinghasnotbeenaseasyasintheearlieryearsofabalonecultureinChina.Ononehandlargequantitiesofpostlarvaeaftersettlement(<20days)talloffthesubstrateanddie.Ontheotherhandlotsofyoungjuvenilesdiewhentheyareremovedfromsubstratetohorizontalrearing--usuallywithin15daysorso.Theseproblemsoccurinthenorthandsouth,resultinginarequirementformorefrequentspawning.Since1995,inthenorth,acrossbreedingoflocalH.discusshannaiwiththesamespeciesintroducedfromJapanhasgeneratedimprovementsinthisphaseofculture.Unfortunatelytheimprovementswerenotsustainedforanylongerthan2-3y(WangQ.,pers.com.2001)andforthisreasonsomehavebelievedthatthespecieshasdegeneratedbyinbreedingafteralongtermofartificialculture.
Grow-out,Density,Cycle,OutputandMarketSize
Inthenorth,aspecialcageforabalonecultureisusedwith400-600seed(at>15mm)pertieratthestartofthegrowoutcycle.Theseanimalsarethenscatteredintoothercagestoreducestockingdensityfourtimesinthe2-3yoftheculturecycle.Whentheyreachsizeclassesof>55mmand75mmtheyaresoldtodomesticandoverseasmarketsrespectively.Forthisphasetheraftsusedhang25-30stacksandastackof12tierscrops25-30kgofmarketsizeabalone(WangQ.,pers.2001).
Inthesouth,aplasticbasketisusedintankculturefor30-35individualanimalsof20-mmshelllength.Theyarethengrowninthisbaskettomarketsize.Somefarmsraise50individualsinthisbasketatthestartandthenscatterthemtogive30individualswhentheyreach30-mmshelllength.Acyclefrom20mmto>50mmtakesabout6-8mo.Atpresentthesmallabaloneareconsumedat90individualsperkg(about47mmshelllength)inthesouthernmarkets.Abasketcrops400ginthis6-8mo.Percubicmeterofwatercapacitythereare24-30baskets,cropping9-12kg.Meansurvivalisabout75%(Nie&Wang2000,Nie&Wang2001).
Theconcretecasesusedinthesouthforintertidalcultureraise500-700juvenilesat10-20mmshelllengthandharvest6-7.5kginaround9-12mo.Thesurvivalrateisabout50%to60%(QiuC.W.,pers.comm.2001).
Food
Chinaisacountryinwhichabundantculture,ofalgaesuchasLaminariajaponicaandUndariapinnatifidaoccurs.NaturalresourcesofGracilariatenuistipitataaboundinthesouth.ThebrownandredalgaearefavoritesofH.discushannaiandH.diversicolouraquatilisrespectively.Thefeedingha
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